Ultraviolet light having a wavelength in a range from 180 to 300 nm has been used for the disinfection of air, water, and surfaces for many years. Wavelengths near 253.7 nm are particularly useful for killing bacteria, viruses, fungus, mold, and spores, and are conveniently generated by low pressure mercury vapor lamp. Many devices and methods for utilizing UV for disinfection include devices for use in HVAC equipment for treatment of air streams and surfaces. However, these related art devices have not adequately addressed safety and performance issues.
“Disinfection” refers to killing pathogenic or otherwise undesirable micro-organisms. Products using short-wave ultraviolet radiation with wavelengths in the range of 180 to 350 nm have been used to disinfect air streams in residential and commercial HVAC systems. This is a high energy form of radiation that is not visible to humans. While this high energy ultraviolet light is capable of destroying a variety of biological pathogens and non-pathogenic, but nevertheless undesirable organisms, it is also hazardous to humans. Short wavelength ultraviolet radiation has been determined to be the cause of skin cancers, such as melanoma, and some cases of non-Hodgkin's lymphoma by the National Center for Chronic Disease Prevention at the Centers for Disease Control and Prevention and by the National Cancer Institute. The eyes are particularly susceptible to damage caused by ultraviolet radiation. The upper threshold for exposure of the human eye to ultraviolet light has been set at 3 millijoules per square centimeter.
The lamps typically used to produce ultraviolet radiation for germicidal application produce a flux of ultraviolet radiation, well in excess of this threshold and, often 100 to 1000 times higher than this threshold. Therefore, protective measures should be taken to protect workers and consumers who use ultraviolet light for germicidal applications.
Protective eyewear can adequately protect workers from health risk while working with ultraviolet devices. However, examination of Worker's Compensation Insurance claims reveal that one-half of the ultraviolet radiation related eye injuries occurred to workers who were in possession of, but neglected to use, proper protective eyewear.
In the past, sterilization and disinfection units were inadequately protected. While some units have electrical or mechanical mechanisms that may shut off a UV emitting germicidal lamp when it is removed from its enclosure, the device may be energized prior to installation, thereby subjecting the user or service person installing the unit to ultraviolet radiation.